1. Technical Field
The present invention relates to a method for producing di(2-ethylhexyl) terephthalate, and more particularly, to a method for producing di(2-ethylhexyl) terephthalate using a chelated catalyst of titanium or zirconium.
2. Background Technology
Di(2-ethylhexyl) terephthalate (also called diisooctyl terephthalate, DOTP for short) is a nontoxic plasticizer applicable to food containers and features good compatibility with polymeric materials such as polyvinyl chloride (PVC), low volatility, and excellent electric properties. DOTP may be prepared from 2-ethylhexanol and terephthalic acid (TPA) under pressurized conditions in the presence of a catalyst.
In the prior art, in order to increase the efficiency of esterification of terephthalic acid, for example, Japanese Patent Publication No. JP2004300078A, a technology is disclosed, where during the esterification for preparing terephthalic acid di-esters, a high boiling point solvent is used to increase the esterification temperature, which accelerates the esterification.
Furthermore, the aforesaid esterification of terephthalic acid is an equilibrium reaction; if the byproduct water produced in the production can be removed from the reaction, the equilibrium will remove towards the product side (i.e. ester side); and if water is not removed from the reaction system during the reaction, not only the catalyst is deactivated, but also the reaction becomes very slow after the equilibrium movement reaches a certain conversion rate. To solve this problem, for example, Chinese Patent CN1225455C disclosed a method for producing polybasic acid esters, where in the reaction zone in the presence of an esterification catalyst, an acid or its anhydride and an alcohol component are heated, and during the reaction, the vapor containing the alcohol and water is separated into an alcohol rich distillate and a water rich distillate by vapor distillation. The alcohol rich distillate is returned back to the reaction zone and the water rich distillate exits the reaction process. As such, the essentially quantitative conversion rate can be rapidly adjusted.
Currently, good methods for preparing DOTP are still badly needed and have yet to be further developed.